There have been active matrix display devices in which a plurality of pixels is arranged in matrix, and a switching transistor and a display element which is connected to the switching transistor are provided for each pixel.
As a switching transistor preferable for the active matrix display device, a transistor including a channel formation region including metal oxide has drawn attention (Patent Documents 1 and 2). Further, as examples of a display element applicable to the active matrix display device, a liquid crystal element, electronic ink using an electrophoresis method, and the like can be given.
Active matrix display devices using liquid crystal elements have been used in wide application from moving image display taking advantage of high operation speed of the liquid crystal element to still image display with a wide range of gray levels.
Active matrix display devices using electronic ink have been used for display devices with extremely low power consumption, taking advantage of so-called memory properties, a feature of the electronic ink, by which a displayed image is kept even after power supply is stopped.